**5. A future glimpse into the environmental history of marine mammals**

Many centuries ago, the Atlantic experienced a (near) pristine situation regarding ocean environmental equilibrium. Levels of the populations of predators and prey were relatively stable and fluctuated naturally. Natural disasters happened with much more localized effects and the impacts of climatic shifts were gradual and predictable. Marine resources were historically exploited, however, until the advent of industrialization, rapid depletion and ecological tipping effects were hindered by lack of technological advances. Industrial Revolution provided the combination of sudden increases in manpower accompanied by new tools and technology which caused overfishing, produced changes in the environment, and cause shifts in ecosystem services and global cycles. The impacts of anthropogenic actions have accelerated in the last decades and are ubiquitous, fast and intense, and exceed the ability of the natural world´s adaptation potential. However, the history of human interactions with marine environments remains largely unstudied. The marine environmental history is, now, a useful tool to understand the past ecological and cultural Human driven transformations in oceans worldwide at small and large spatial and temporal scales.

Marine mammals (either whales, dolphins, and seals, or even manatees and dugongs) represent good case studies for the single-species approach to marine environmental history. The two case-studies presented in this chapter are an example of the valuable outcomes of an interdisciplinary analysis to recreate the environmental history of marine mammals. This history can then be used to frame present traditions as well as population levels of mammals.

The future of marine environmental historians, dedicated to the study of marine mammals, will greatly benefit from focusing on the research of the relation of people with species, with special interest in specific economic and/or cultural isolated situations, such as African and Brazilian manatees, or cetaceans' historical presence around oceanic islands. For instance, historically in some Atlantic cultures, cetaceans were considered "a different kind of fish", as their recognisable natural behaviour and some morphological characteristics are distinct from fish [53]. Studies related to local perceptions changing over time can also provide inputs to the environmental history of marine mammals and contribute for the implementation of long-term and continuous scientific research, interactive environmental education plans and conservation measures. This type of research may include different kinds of historical sources, such as written, iconographic or material sources, and all types of accounts from the period since the late 15th century. European reports of Atlantic (or other oceanic basins) journeys contain information about natural elements and marine mega fauna and represent invaluable sources of research. For a later period (from late 19th century onwards), scientific articles, newspapers, illustrations, maps, non-published scientific reports and some other grey literature, such as unpublished thesis, may also be used. Good history begins with good sources [3], but good marine environmental history needs also to be framed into interdisciplinary boundaries.
